Field
A positive active material for a rechargeable lithium battery, a positive electrode including the same, and a rechargeable lithium battery are disclosed.
Description of the Related Art
Recently, rechargeable lithium batteries have been drawing a lot of attention as power sources for portable small electronic devices which have advantageous characteristics of high-capacity and lightness and thus, are used for almost all cordless devices. Rechargeable lithium batteries are used for portable phones, laptops and the like and also, cordless tools such as an electric drills and the like.
In general, rechargeable lithium batteries are manufactured by inserting an electrode assembly along with an electrolyte solution into a battery case and sealing the top opening of the battery case with a sealing member, and the electrode assembly includes a negative electrode including a negative active material, a positive electrode including a positive active material, a separator, and the like.
The positive active material for a rechargeable lithium battery is a constituent element capable of determining energy density and output density of the rechargeable lithium battery. Lithium cobalt oxide (LiCoO2) is used as a positive active material for a rechargeable lithium battery as a power source for a portable electronic device but has not been applied yet to a high energy rechargeable lithium battery for an electric vehicle due to structural/thermal stability, high price, and toxicity. Accordingly, an alternative positive active material replacing the LiCoO2 has been much researched/developed, and as a result, LiNi1/3Mn1/3CO1/3O2, LiNi0.8Co0.15Al0.05O2, LiMn2O4, LiFePO4, and the like are currently used as a positive active material for the electric vehicle batteries. However, these positive active materials have capacity of less than or equal to about 200 mAh/g and do not satisfy energy density required of the electric vehicle.
Accordingly, development of a positive active material having higher capacity than the conventional positive active materials has drawn interest, and recently, a Li-rich layered oxide has been actively researched for commercial availability as the positive active material for an electric vehicle due to an advantage of high capacity of greater than or equal to about 250 mAh/g and price.
The commercial availability of the Li-rich layered oxide may be accomplished by improving various characteristics occurring during a cycle life such as a voltage decrease phenomenon, energy density per volume, a cycle-life, and the like. The voltage decrease phenomenon occurring during the cycle-life should be solved for the commercial availability of the Li-rich layered oxide.